This invention relates to a method and apparatus for hardening thermally the heads of steel railroad rails to increase the service life of the rails.
Techniques have previously been evolved for hardening rail heads and typical of these are the techniques disclosed in Canadian Pat. Nos. 744,688 and 888,671. In both cases the rail is heated and quenched progressively along the head by causing the rail to move axially with respect to heating and quenching devices. Because such heat treatment would cause the rail to assume a final distorted condition in which the head would have an upward concave curvature, mechanical forces are applied to the rail simultaneously with the heat treatment to bend the rail so that it has a downward concave curvature which cancels the upward concave curvature obtained on quenching.
The major drawback of these prior techniques is that they must be carried out in the workshop prior to laying the track and so a further delay in the manufacture of heat hardened rails ready for laying is provided. Furthermore, these techniques can only be used economically on new rails in view of the expense of lifting and relaying existing track.